The present invention relates to end caps for coalescer or filter cartridges.
Coalescers and filter cartridges are generally manufactured in cylindrical form and comprise a selected medium or media for the removal of undesirable contaminants. The media generally requires a structural member to support it, and the media must be sealed at the ends to prevent passage of fluid around the ends of the media rather than passing through it. Generally, some type of rigid disc-like member, having a bore or opening corresponding to the desired bore of the cartridge, is provided and the filter or coalescing medium or media is secured thereto. Such an end cap or disc may be molded of plastic or formed of metal and shaped as to form a reservoir which contains the adhesive for bonding the media and structural member to the end cap. It is common practice to attach a gasket to the end cap on the side opposite that to which the media is adhered so as to form a seal between the end cap of the cartridge and the stool on which the cartridge is mounted. Sometimes, the material used as the adhesive may be molded to form the end cap itself, thereby eliminating a separate end cap. In this case, the gasket is integral with the molded end cap.
Coalescer/filter cartridges have as a primary function the removal of solid contaminants and/or coalescing immiscible fluids one from another. The media by which the contaminant, either solid or liquid, is removed may take the form of a pleated surface, a surface of multiple pleats, a cylindrical surface, or a cylindrical mass of selected depth. These media prevent the passage of solids or liquid droplets, such as would be the case in a hydrophobic membrane, or permit the passage of the liquid but entrap the solid particles so as to prevent their passage through the medium or media. Coalescing media opposes the direct flow of a small liquid droplet and retains it within the medium until it has the opportunity to join with other similar droplets thereby forming larger droplets due to the cohesive action between one droplet and another. This formation of larger droplets, either due to impaction or compaction of one droplet against another, is the principle on which coalescence is based.
Coalescer/filter cartridges are generally made in cylindrical form and include end caps having an outside diameter and an inside diameter between which is the area to which the coalescing/filtering media or medium is attached. The dimension between the inner and outer diameters determines the amount of coalescer/filter medium or media which may be used in a given filter cartridge. Again, since the purpose of the media is to prevent the passage of undesirable contaminants, the ends of the media must be sealed to prevent the passage of fluid around them. Typically, this seal is accomplished by metal, plastic, or paper end caps or discs designed so as to form a shallow reservoir into which the adhesive is applied for the attachment of the coalescer/filter media to the impervious end cap. This end cap or disc accommodates the attachment of a gasket seal on the surface opposite that of the adhesive reservoir for adherence of the media to the end cap. A typical cartridge has an outer diameter of approximately six inches and an inner diameter of approximately three and one-half inches.
The central opening of the end cap and that of the cartridge is placed over the cartridge mounting stool upstanding extension, which has the purpose of positioning the cartridge so that the central axis for the cartridge coincides with the axis of the cartridge mounting stool. The cartridge mounting stool includes a surface orthogonal to the stool axis for the purpose of sealing against the cartridge gasket. Axial load is then applied to the end of the cartridge to provide a tight seal against the gasket. The integrity of this seal is important to insure that all fluid passes through the coalescing/filter medium.
A drawback to filter cartridges having end caps of this type is that the amount of filter or coalescing media is dictated by the inner and outer diameters of the end cap. To increase the area of pleated media or to increase the volume of depth type media, it is necessary to reduce the inside diameter of the end cap opening so that the media can be adequately supported and sealed on its ends. In the case of prior art end caps, however, a problem arises in reducing the inner diameter thereof because of the upstanding extension portion of the mounting stool, which extends through the end cap bore. With prior art end caps, the minimum inner diameter is limited to the outer diameter of the mounting stool extension, thereby limiting the amount of filtering or coalescing media contained within the cartridge.